Photographic elements are desirably provided with one or more conductive antistatic layers to prevent undesirable static discharges during manufacture, exposure and processing of the photographic element. Antistats proposed for use in photographic elements include non-film forming particulate materials comprising metal oxides, for example, tin oxide, antimony doped tin oxide, vanadium pentoxide, and metal antimonate particles. Such particulate materials are generally coated in a thin layer at relatively high loading levels relative to any film forming binder in order to provide good antistatic performance while maintaining photographic transparancy. In order to provide good adhesion to a photographic element support, such highly loaded antistatic layers have generally been coated directly over a thin subbing layer on the support. Such antistatic layers are conventionally typically coated on the opposite side ("back-side") of the support relative to the light-sensitive layers of the photographic element. Particular antistatic layer formulations are disclosed in, e.g., U.S. Pat. Nos. 4,203,769, 4,394,441, 4,418,141, 4,495,278, 5,368,995.
It is also known to include in various kinds of imaging elements a transparent magnetic recording layer containing magnetic particles dispersed in a polymeric binder. The inclusion and use of such transparent magnetic recording layers in light-sensitive silver halide photographic elements has been described in, e.g., U.S. Pat. Nos. 3,782,947; 4,279,945; 4,302,523; 5,217,804; 5,229,259; 5,395,743; 5,413,900; 5,427,900; 5,498,512; and others. Such elements are advantageous because images can be recorded by customary photographic processes while information can be recorded simultaneously into or read from the magnetic recording layer by techniques similar to those employed for traditional magnetic recording art.
The transparent magnetic recording layer must be capable of accurate recording and playback of encoded information repeatedly on demand by various devices such as a camera or a photofinishing or printing apparatus. Said layer also must exhibit excellent running, durability (i.e., abrasion and scratch resistance), and magnetic head-cleaning properties without adversely affecting the imaging quality of the photographic elements. However, this goal is extremely difficult to achieve because of the nature and concentration of the magnetic particles required to provide sufficient signal to write and read magnetically stored data and the effect of any noticeable color, haze or grain associated with the magnetic layer on the optical density and granularity of the photographic layers. These goals are particularly difficult to achieve when magnetically recorded information is stored and read from the photographic image area. Further, because of the curl of the photographic element, primarily due to the photographic layers and the core set of the support, the magnetic layer must be held more tightly against the magnetic heads than in conventional magnetic recording in order to maintain planarity at the head-media interface during recording and playback operations. Thus, all of these various characteristics must be considered both independently and cumulatively in order to arrive at a commercially viable photographic element containing a transparent magnetic recording layer that will not have a detrimental effect on the photographic imaging performance and still withstand repeated and numerous read-write operations by a magnetic head.
Problems associated with the formation and discharge of electrostatic charge during the manufacture and utilization of photographic film and paper have been recognized for many years by the photographic industry as discussed above. In films comprising a transparent magnetic recording layer which are designed to be used in automatic cameras, because of the repeated motion of a photographic roll film in and out of a film cassette, there is the added problem of the generation of electrostatic charge by the movement of the film across magnetic heads and by the repeated winding and unwinding operations, especially in a low relative humidity environment. The accumulation of charge on the film surface results in the attraction and adhesion of dust to the film. The presence of dust not only can result in the introduction of physical defects and the degradation of the image quality of the photographic element but also can result in the introduction of noise and the degradation of magnetic recording performance (e.g., S/N ratio, "drop-outs", etc.). This degradation of magnetic recording performance can arise from various sources including signal loss resulting from increased head-media spacing, electrical noise caused by discharge of the static charge by the magnetic head during playback, uneven film transport across the magnetic heads, clogging of the magnetic head gap, and excessive wear of the magnetic heads. Accordingly, the use of a conductive antistatic layer in photographic elements comprising transparent magnetic recording layers is especially important. Typically, in photographic elements of prior art comprising a transparent magnetic recording layer, the antistatic layer is present as a backing layer underlying the magnetic recording layer (see, e.g., U.S. Pat. No. 5,457,013).
It is also frequently desirable to coat one or more curl control layers on the back-side of the support of a photographic film element comprising light-sensitive layers in order to prevent excessive curl in the element upon drying of the coated light-sensitive layers, to ensure the film element remains sufficiently flat in a camera or printer during exposure and printing to optimize focus conditions, as well as to facilitate transport of the film through a camera and processing apparatus. Such back-side curl control layers typically comprise a hydrophilic binder coated from an aqueous formulation, and are of sufficient total thickness upon drying (generally from 1-25 micrometers) to off-set the curl generated by the hydrophilic binder layers on the light-sensitive emulsion layer side of the support to a desired degree. Use of curl control layers is especially important where a transparent magnetic recording layer is included in relatively wide (i.e., wider than 35 mm) roll camera films, such as 120 and 220 medium format films, and sheet films including as x-ray and graphic arts films, as such films are generally more sensitive to curl and the resulting degradation of magnetic recording performance associated with variable head-media spacing. Optimized ratios of the thicknesses of light sensitive layers, magnetic recording layers, and curl control layers comprising hydrophilic colloids in photographic elements for curl control are described, e.g., in copending, commonly assigned U.S. Ser. No. 08/604,272, now U.S. Pat. No. 5,753,426 the disclosure of which is incorporated by reference herein.
Adhesion of a backing layer arrangement comprising a substantial curl control layer package in addition to a magnetic recording layer coated over a highly filled (i.e., low binder), relatively thin antistatic layer on a film support can be problematic where the antistatic layer is coated directly on a support or over a thin primer layer (such as a vinylidene chloride based copolymer layer) as is commonly practiced in the art. It would be advantageous to be able to provide curl control, magnetic recording, and highly filled antistatic layers in a film element which exhibited good adhesion performance. It would further be desirable to provide such a film element wherein such layers are effectively simultaneously coatable from aqueous coating compositions in a single coating pass.